Malignant mesotheliomas are of three cell types:

When a patient has symptoms suggesting malignant mesothelioma, a doctor starts with imaging techniques to confirm a diagnosis. Depending on the cell type, a diagnosis of malignant mesothelioma can be made. Malignant mesotheliomas are of three cell types: epithelioid, mixed and sarcomatoid. In general, epithelioid malignant mesotheliomas are the most common and carry the best prognosis; sarcomatoid ones are the most rare.

Epithelial mesothelioma is the most common type of malignant mesothelioma. Patients with this form of cancer may respond more favourably to treatment. An epithelioid cell is a mesenchymal cell whose morphology resembles that of epithelial cells. An important point to note is that malignant epithelioid mesothelioma cells very closely resemble cells of another type of cancer known as adenocarcinoma.